JP2016180905A - Transfer member and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce discharge between a transfer member and a driving member facing the transfer member, while stably driving an image holding body in an endless strip shape over time with the driving member.SOLUTION: There is provided an image forming apparatus (U) comprising: an image holding body (B) in an endless strip shape having an image held on its surface; a driving member (T2a) that supports the image holding body (B) and rotates the image holding body (B) upon transmission of drive from a driving source; a transfer member (T2b) that is arranged opposite to the driving member (T2a) with the image holding body (B) therebetween and transfers the image on the surface of the image holding body (B) to a medium (S), the transfer member (T2b) including a conductive base part (1), and a surface layer (3) that covers the surface of the base part (1) and has a higher volume resistivity than that of the base part, where the length in the axial direction of the surface layer (3) is longer than the length in the axial direction of the base part (1).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a transfer member and an image forming apparatus.

  In a conventional image forming apparatus such as an electrophotographic copying machine or printer, a technique described in Patent Document 1 below is known regarding a transfer member.

  In Japanese Patent Application Laid-Open No. 2000-221809 as Patent Document 1, an intermediate transfer belt (121) is supported by a drive roller (124), a secondary transfer counter roller (126) different from the drive roller (124), or the like. In addition, the image on the intermediate transfer belt (121) is transferred to the transfer paper (100) by the secondary transfer roller (131) facing the secondary transfer counter roller (126) with the intermediate transfer belt (121) interposed therebetween. Is described. In the technique described in Patent Document 1, the diameter of the secondary transfer roller (131) becomes smaller as the elastic layer (131e) goes to the end in the axial direction in order to reduce the shortage of axial contact pressure. It is configured as follows.

JP 2000-221809 (“0018” to “0019”, “0023” to “0024”, “0040”, FIGS. 1 and 3)

  It is a technical object of the present invention to reduce discharge between a transfer member and a drive member while stably driving an endless belt-shaped image carrier with time by a drive member facing the transfer member. .

In order to solve the technical problem, an image forming apparatus according to claim 1 is provided.
An endless belt-shaped image carrier on which an image is held on the surface;
A driving member that supports the image carrier and rotates the image carrier by being driven by a drive source;
A transfer member disposed opposite to the driving member with the image carrier interposed therebetween, and transferring the image on the surface of the image carrier to a medium, covering a conductive base and the surface of the base; A surface layer having a volume resistivity higher than that of the base, and the transfer member in which the axial length of the surface layer is formed longer than the axial length of the base, and
It is provided with.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The protruding amount of the surface layer protruding from the axial end of the base portion is set to a length of 2.75 mm or more and not more than the thickness of the surface layer.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The base having a chamfered end in the axial direction;
It is provided with.

In order to solve the technical problem, the transfer member of the invention according to claim 4,
A transfer member disposed opposite to the drive member for rotating the endless belt-shaped image holding member with the image holding member interposed therebetween, and transferring the image on the surface of the image holding member to a medium;
A conductive base;
A surface layer covering the surface of the base and having a higher volume resistivity than the base, the surface layer being formed longer than the axial length of the base; and
It is provided with.

According to the first and fourth aspects of the present invention, the driving member facing the transfer member is shorter than the case where the axial length of the surface layer is shorter than the axial length of the base portion. Thus, the discharge between the transfer member and the drive member can be reduced while the endless belt-shaped image carrier is driven stably over time.
According to the second aspect of the present invention, it is possible to prevent the rubber from tearing while suppressing discharge as compared with the case where the protruding amount is less than 2.75 mm or larger than the thickness of the surface.
According to the third aspect of the present invention, it is possible to suppress discharge compared to the case where chamfering is not performed.

FIG. 1 is an overall explanatory view of an image forming apparatus according to a first embodiment. FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to the first embodiment. FIG. 3 is an enlarged explanatory view of a main part of the secondary transfer region of the first embodiment. FIG. 4 is an explanatory diagram of the secondary transfer roll according to the first embodiment. FIG. 5 is an explanatory diagram of the experimental results of the experimental example.

Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as front, rear, right, left, upper, lower, or front, rear, right, left, upper, and lower, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to a first embodiment.
FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to the first embodiment.
In FIG. 1, a copier U as an example of an image forming apparatus according to a first exemplary embodiment of the present invention is an example of a recording unit, and includes a printer unit U1 as an example of an image recording apparatus. A scanner unit U2 as an example of a reading unit and an example of an image reading device is supported on the upper portion of the printer unit U1. An auto feeder U3 as an example of a document transport device is supported on the upper portion of the scanner unit U2. The scanner unit U2 of the first embodiment supports a user interface UI as an example of an input unit. The user interface UI can be operated by the operator by inputting the user interface UI.

  A document tray TG1 as an example of a medium container is disposed on the upper part of the auto feeder U3. A plurality of documents Gi to be copied can be stacked and stored in the document tray TG1. A document discharge tray TG2 as an example of a document discharge unit is formed below the document tray TG1. A document transport roll U3b is disposed between the document tray TG1 and the document discharge tray TG2 along the document transport path U3a.

A platen glass PG as an example of a transparent document table is disposed on the upper surface of the scanner unit U2. In the scanner unit U2 of the first embodiment, a reading optical system A is disposed below the platen glass PG. The optical system A for reading in Example 1 is supported so as to be movable in the left-right direction along the lower surface of the platen glass PG. The reading optical system A is normally stopped at the initial position shown in FIG.
An imaging member CCD as an example of a reading member is disposed on the right side of the reading optical system A. An image processing unit IPS is electrically connected to the imaging member CCD.

The image processing unit IPS is electrically connected to the writing circuit DL of the printer unit U1. The writing circuit DL is an example of a latent image forming apparatus, and is electrically connected to LED heads LHy, LHm, LHc, and LHk as an example of an exposure apparatus.
The LED heads LHy, LHm, LHc, and LHk of Example 1 are arranged corresponding to each color of Y, M, C, and K. Note that the LED heads LHy to LHk of Example 1 are configured by an LED array in which LEDs as an example of light emitting elements are linearly arranged along the width direction of an image. The LED heads LHy to LHk are configured so that the LEDs can emit light in accordance with an input signal. That is, the LED heads LHy to LHk are configured to be able to output writing light according to the input signal.

In FIG. 1, photoconductors PRy, PRm, PRc, and PRk, which are examples of image carriers, are disposed above the LED heads LHy to LHk. The write areas Q1y, Q1m, Q1c, and Q1k are configured by areas where the photoconductors PRy to PRk and the LED heads LHy to LHk face each other.
Charging rolls CRy, CRm, CRc, and CRk as an example of a charger are disposed upstream of the LED heads LHy to LHk with respect to the rotation direction of each of the photoconductors PRy, PRm, PRc, and PRk. The charging rolls CRy to CRk of Example 1 are supported so as to be driven to rotate in contact with the photoreceptors PRy to PRk.
Developing devices Gy, Gm, Gc, and Gk are disposed on the downstream side of the LED heads LHy to LHk with respect to the rotation direction of the photoconductors PRy to PRk. Development regions Q2y, Q2m, Q2c, and Q2k are configured by regions where the photoconductors PRy to PRk and the developing devices Gy to Gk face each other.

Primary transfer rolls T1y, T1m, T1c, and T1k as an example of a primary transfer unit are disposed on the downstream side of the developing devices Gy to Gk with respect to the rotation direction of the photosensitive members PRy to PRk. The primary transfer regions Q3y, Q3m, Q3c, and Q3k are configured by regions where the photoconductors PRy to PRk and the primary transfer rolls T1y to T1k face each other.
Photoreceptor cleaners CLy, CLm, CLc, and CLk as an example of an image carrier cleaner are disposed downstream of the primary transfer rolls T1y to T1k with respect to the rotation direction of the photoreceptors PRy to PRk. .

  The Y color of Example 1 in which a toner image as an example of a visible image is formed by the Y color photoreceptor PRy, the charging roll CRy, the LED head LHy, the developing device Gy, the primary transfer roll T1y, and the photoreceptor cleaner CLy. A Y-color image forming unit Uy as an example of the visible image forming apparatus is configured. Similarly, each photoconductor PRm, PRc, PRk, charging roll CRm, CRc, CRk, LED head LHm, LHc, LHk, developing device Gm, Gc, Gk, primary transfer roll T1m, T1c, T1k, photoconductor cleaner CLm. , CLc, CLk constitute the image forming portions Um, Uc, Uk of the M, C, K colors.

Above the photoconductors PRy to PRk, a belt module BM as an example of an intermediate transfer device is disposed. The belt module BM is an example of an image carrier, and includes an intermediate transfer belt B as an example of an intermediate transfer member. The intermediate transfer belt B is composed of an endless belt-like member.
The intermediate transfer belt B according to the first exemplary embodiment includes a tension roll Rt as an example of a stretching member, a walking roll Rw as an example of a member that corrects a deviation, an idler roll Rf as an example of a driven member, and a secondary roll. It is an example of an opposing member in the transfer region, and is rotatably supported by a backup roll T2a as an example of a drive member and primary transfer rolls T1y, T1m, T1c, and T1k.

A secondary transfer roll T2b as an example of a secondary transfer member is disposed at a position facing the backup roll T2a across the intermediate transfer belt B. In Embodiment 1, a secondary transfer voltage having the same polarity as the toner charging polarity is applied from the power supply circuit E to the backup roll T2a, and the secondary transfer roll T2b is grounded. The backup roll T2a and the secondary transfer roll T2b constitute the secondary transfer device T2 of the first embodiment. Further, the secondary transfer region Q4 is constituted by the region where the secondary transfer roll T2b and the intermediate transfer belt B are in contact with each other.
A belt cleaner CLb is disposed on the downstream side of the secondary transfer region Q4 with respect to the rotation direction of the intermediate transfer belt B as an example of an intermediate transfer member cleaner.
The primary transfer rolls T1y to T1k, the intermediate transfer belt B, the secondary transfer unit T2, and the like constitute a transfer device T1 + T2 + B of the first embodiment. The image recording units Uy to Uk + T1 + T2 + B of the first embodiment are configured by the image forming units Uy to Uk and the transfer device T1 + T2 + B.

In FIG. 1, three pairs of left and right guide rails GR as an example of a guide member are provided below the image forming units Uy to Uk. On each guide rail GR, paper feed trays TR1 to TR3, which are examples of medium accommodating portions, are supported so as to be able to enter and exit in the front-rear direction. Recording sheets S as an example of a medium are accommodated in the paper feed trays TR1 to TR3.
A pickup roll Rp, which is an example of a take-out member, is disposed on the upper left side of the paper feed trays TR1 to TR3. A separating roll Rs as an example of a separating member is disposed downstream of the pickup roll Rp with respect to the conveyance direction of the recording sheet S. As an example of a medium transport path, a paper feed path SH1 extending upward is formed on the downstream side of the separation roll Rs with respect to the transport direction of the recording sheet S. A plurality of transport rolls Ra as an example of a transport member is disposed in the paper feed path SH1.

In the sheet feeding path SH1, a registration roll Rr as an example of a conveyance timing adjusting member is disposed on the upstream side of the secondary transfer region Q4.
A fixing device F is disposed on the downstream side of the secondary transfer region Q4 with respect to the conveyance direction of the sheet S. The fixing device F includes a heating roll Fh as an example of a fixing member for heating and a pressure roll Fp as an example of a fixing member for pressure. A fixing region Q5 is constituted by a contact region between the heating roll Fh and the pressure roll Fp.
Above the fixing device F, a paper discharge path SH2 as an example of a transport path is disposed. A paper discharge tray TRh as an example of a medium discharge unit is formed on the upper surface of the printer unit U1. The paper discharge path SH2 extends toward the paper discharge tray TRh. A paper discharge roll Rh, which is an example of a medium transport member, is disposed at the downstream end of the paper discharge path SH2.

(Description of image forming operation)
In the copying machine U according to the first embodiment having the above-described configuration, when the copying operation is started, the plurality of documents Gi stored in the document tray TG1 sequentially pass through the document reading positions on the platen glass PG, The document is discharged to a paper discharge tray TG2.
When the automatic feeder U3 is used to automatically convey and copy a document, each document that sequentially passes through the reading position on the platen glass PG with the reading optical system A stopped at the initial position. Gi is exposed. When the operator places the document Gi on the platen glass PG by hand, the optical system A for reading moves in the left-right direction, and the document on the platen glass PG is scanned while being exposed.
Reflected light from the original document Gi passes through the optical system A for reading and is condensed on the imaging member CCD. The imaging member CCD converts the reflected light of the document Gi focused on the imaging surface into an electrical signal.

The image processing unit IPS receives an electrical signal output from the imaging member CCD. The image processing unit IPS converts the electrical signals of the R, G, and B color images read by the imaging member CCD into image information of yellow Y, magenta M, cyan C, and black K for forming a latent image. The image processing unit IPS outputs the converted image information to the writing circuit DL of the printer unit U1. Note that the image processing unit IPS outputs image information of only black K to the writing circuit DL when the image is a monochrome image, so-called monochrome.
The writing circuit DL outputs a control signal corresponding to the input image information to the LED heads LHy to LHk. The LED heads LHy to LHk output writing light according to the control signal.

  Each of the photoconductors PRy to PRk is driven to rotate when image formation is started. A charging voltage is applied from the power supply circuit E to the charging rolls CRy to CRk. Therefore, the surfaces of the photoconductors PRy to PRk are charged by the charging rolls CRy to CRk. Electrostatic latent images are formed on the surfaces of the charged photoconductors PRy to PRk by writing light from the LED heads LHy to LHk in the writing areas Q1y to Q1k. The electrostatic latent images on the photoconductors PRy to PRk are developed into toner images as an example of visible images by the developing devices Gy, Gm, Gc, and Gk in the development areas Q2y to Q2k.

The developed toner image is conveyed to primary transfer regions Q3y, Q3m, Q3c, and Q3k that are in contact with the intermediate transfer belt B. In the primary transfer regions Q3y, Q3m, Q3c, and Q3k, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the power supply circuit E to the primary transfer rolls T1y to T1k. Accordingly, the toner images on the photoconductors PRy to PRk are transferred to the intermediate transfer belt B by the primary transfer rolls T1y to T1k. In the case of a multi-color toner image, the downstream toner image is transferred so as to overlap the toner image transferred to the intermediate transfer belt B in the upstream primary transfer region.
Residues and deposits on the photoconductors PRy to PRk after the primary transfer are cleaned by the photoconductor cleaners CLy to CLk. The cleaned surfaces of the photoconductors PRy to PRk are recharged by the charging rolls CRy to CRk.
The single-color or multicolor toner images transferred onto the intermediate transfer belt B by the primary transfer rolls T1y to T1k in the primary transfer areas Q3y to Q3k are conveyed to the secondary transfer area Q4.

The sheet S on which an image is recorded is taken out by the pickup rolls Rp of the paper feed trays TR1 to TR3 to be used. The sheets S picked up by the pick-up roll Rp are separated one by one by the rolls Rs when a plurality of sheets S are picked up. The sheet S separated by the separating roll Rs is conveyed through the sheet feeding path SH1 by the conveying roll Ra. The sheet S conveyed through the sheet feeding path SH1 is sent to the registration roll Rr.
The registration roll Rr conveys the sheet S to the secondary transfer area Q4 at the same time when the toner image formed on the intermediate transfer belt B is conveyed to the secondary transfer area Q4. A secondary transfer voltage having the same polarity as the toner charging polarity is applied to the backup roll T2a by the power supply circuit E. Therefore, the toner image on the intermediate transfer belt B is transferred from the intermediate transfer belt B to the sheet S.

The intermediate transfer belt B after the secondary transfer is cleaned of deposits and the like adhering to the surface by the belt cleaner CLb.
The recording sheet S on which the toner image has been secondarily transferred is heated and fixed when passing through the fixing region Q5.
The recording sheet S on which the image is fixed is conveyed through the paper discharge path SH2. The sheet S conveyed through the paper discharge path SH2 is discharged to the paper discharge tray TRh by the paper discharge roll Rh.

(Description of intermediate transfer device)
FIG. 3 is an enlarged explanatory view of a main part of the secondary transfer region of the first embodiment.
1-3, a backup roll T2a as an example of a drive member extends in the front-rear direction, which is the width direction of an intermediate transfer belt B as an example of an endless belt-like rotating body. The backup roll T2a according to the first embodiment is driven by a motor M1 as an example of a drive source.
In Example 1, the backup roll T2a is made of durable EPDM rubber so as not to slip with the intermediate transfer belt B over time.

FIG. 4 is an explanatory diagram of the secondary transfer roll according to the first embodiment.
3 and 4, a secondary transfer roll T2b as an example of a transfer member has a shaft portion 1 as an example of a base. In addition, the axial direction edge part of the shaft part 1 of Example 1 is formed in the circular arc shape as an example of chamfering shape, what is called R shape.
In addition, although the shaft part 1 of Example 1 is comprised with the stainless steel as an example of an electroconductive material, it can be changed into arbitrary materials which can be used, such as iron, aluminum, or these alloys.

Shaft portions 2 projecting outward are supported at both ends of the shaft portion 1. The outer end of the shaft portion 2 is rotatably supported by a bearing (not shown). In addition, the axial part 2 of Example 1 is set to the outer diameter of 7 mm.
A rubber tube 3 as an example of a surface layer is supported on the outer periphery of the shaft portion 1. The rubber tube 3 of the first embodiment is formed longer than the axial length of the shaft portion 1. In Example 1, as an example of the rubber tube 3, the volume resistance value is made of urethane rubber having a value of about 7.0 [logΩ] to 7.4 [logΩ]. The rubber tube 3 is not limited to urethane rubber. For example, epichlorohydrin rubber (ECO), acrylonitrile-butadiene rubber (NBR), NBR / ECO mixed rubber, chloroprene rubber (CR), ethylene propylene rubber (EPDM), etc. It can be used.

In Example 1, when the distance from the outer end of the shaft portion 1 to the outer end of the rubber tube 3 is L and the thickness of the rubber tube 3 is t, the following equation (1) is satisfied: A distance L is set.
2.75 [mm] ≦ L ≦ t (1)
When the distance L is shorter than 2.75 mm, electric discharge is easily generated, and when the distance L is larger than the thickness t, the rubber tube 3 is easily broken. In Example 1, as an example, the thickness t = 4.25 mm and the distance (projection amount) L = 3 mm are set.

(Operation of Example 1)
In the copying machine U of Example 1 having the above-described configuration, the secondary transfer roll T2b is formed such that the length of the rubber tube 3 in the axial direction is longer than the length of the shaft portion 1 in the axial direction. Here, in the conventional secondary transfer roll T2b, the length of the rubber tube 3 in the axial direction is shorter than the length of the shaft portion 1 in the axial direction. This is considered to be because there was no reason that the end of the rubber tube 3 was wavy or torn off when the rubber tube 3 was longer, or that the discharge did not occur unless the rubber tube 3 was made longer.

In the conventional image forming apparatus, the driving roll for driving the intermediate transfer belt B is provided separately from the backup roll T2a. Therefore, even if slip occurs between the backup roll T2a and the intermediate transfer belt B, it is difficult to adversely affect the rotation of the intermediate transfer belt B. Therefore, in the conventional configuration, as the backup roll T2a, NBR, urethane rubber (U), which has a relatively high volume resistance value of about 6.3 [logΩ] to 6.7 [logΩ], as the electrical resistance value.
ECO, NBR / ECO mixed rubber, CR were used.
However, these materials are easily worn over time, and slip occurs between the backup roll T2a and the intermediate transfer belt B. Therefore, when the backup roll T2a and the drive roll are shared, there is a problem that the rotation of the intermediate transfer belt B is not stable when the conventional backup roll T2a is used. Therefore, it has become necessary to use EPDM, which is an example of a material capable of securing a friction coefficient with time between the backup roll T2a and the intermediate transfer belt B as the backup roll T2a.

However, with these materials, the friction coefficient can be maintained over time, but there is a problem that the resistance value is relatively low, such as a volume resistance value of 6.0 [logΩ] or less.
Here, in recent years, with the improvement of the number of printed sheets per unit time, so-called productivity, the voltage applied in the secondary transfer region Q4 increases, and the occurrence of transfer defects in the secondary transfer region Q4 is suppressed. .
Therefore, the backup roll T2a and the drive roll are made common, the volume resistivity is lowered, and the voltage applied to the secondary transfer region Q4 is also increased, so that the conventional rubber tube 3 is shorter. In the configuration, end discharge is likely to occur between the backup roll T2a and the shaft portion of the secondary transfer roll T2b. When edge discharge occurs, the voltage set as the secondary transfer voltage does not act, and there is a problem that transfer failure occurs.

On the other hand, in Example 1, the rubber tube 3 having a higher volume resistance value than the shaft portion 1 is formed longer. Therefore, the rubber tube 3 is sandwiched between the shaft portion 1 of the secondary transfer roll T2b and the backup roll T2a, and end discharge is suppressed. Therefore, transfer defects are reduced.
In particular, in Example 1, the end portion of the shaft portion 1 has a chamfered shape. If there is no chamfered shape, it becomes easy to discharge from the corner of the shaft portion 1 as a starting point, but in Example 1 having the chamfered shape, the discharge is further suppressed.

(Experimental example 1)
Next, an experiment was conducted to confirm the effect of the configuration of Example 1 of the present invention.
In Example 1, an experiment was conducted by remodeling Apeosport V C7780 manufactured by Fuji Xerox Co., Ltd. As the backup roll T2a, a member made of EPDM rubber having a diameter of 14.9 [mm] was used. The volume resistance value of the backup roll T2a was 6.0 [logΩ]. The volume resistance value was measured by a flat plate application method. In the flat plate application method, the backup roll T2a is brought into contact with a grounded metal flat plate, and a load of 9.8N (4.9N on one side) is applied to both ends of the backup roll T2a, and the shaft portion 1 of the backup roll T2a is applied. A voltage was applied to and resistance value was measured. Note that the measurement environment was a temperature of 22 ± 3 ° C., a humidity of 55 ± 5%, a voltage of 1 kVDC was applied, and a value 10 seconds after the voltage application was started was measured.
As the shaft portion 1 of the secondary transfer roll T2b, a member made of SUS having an axial length of 320 [mm] and a diameter of 12 [mm] was used.

As the rubber tube 3 of the secondary transfer roll T2b, a urethane tube having a thickness of 4.25 [mm] is used, and a protruding amount L from the end of the shaft portion 1 is 2.5 [mm] to 4.4. Between 75 [mm], the thing of a 0.25 [mm] unit was produced.
In addition, 9.1 kV (DC) was applied as a secondary transfer voltage.
In the experiment, the “discharge suppression effect” is observed by visually observing the light of the discharge, “○” when the light of the discharge is not confirmed, and “×” when the light of the discharge is confirmed. did. In addition, “rubber tear” is a case where the secondary transfer roll T2b after printing equivalent to 200,000 sheets is visually checked, “x” when the rubber is torn, and the case where the rubber is not torn but has a tear. “△”, and “◯” when there was no rubber tear or tear. The experimental results are shown in FIG.

FIG. 5 is an explanatory diagram of the experimental results of the experimental example.
In FIG. 5, in the experiment, the discharge was confirmed when the protrusion amount L was 2.5 [mm] or less, and the discharge was not confirmed when the protrusion amount L was 2.75 [mm] or more. Further, when the protrusion amount L is 4.75 [mm] or more, the rubber is torn, and when the protrusion amount L is 4.5 [mm], a tear is generated, and when the protrusion amount L is 4.25 [mm] or less. No rubber tears were observed. Therefore, it was confirmed that the occurrence of discharge was suppressed and rubber tearing or the like did not occur within the range satisfying the formula (1).

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is made in the range of the summary of this invention described in the claim. Is possible. Modification examples (H01) to (H06) of the present invention are exemplified below.
(H01) In the above-described embodiment, the copying machine U as an example of the image forming apparatus is illustrated. However, the present invention is not limited to this, and can be applied to a printer, a FAX, or a multifunction machine having a plurality of these functions. Further, although a configuration capable of forming images of four colors Y, M, C, and K has been presented, the present invention is not limited to this. The present invention can be applied to an image forming apparatus having three colors or less, a single color, or five colors or more.

(H02) In the above embodiment, the intermediate transfer belt as an example of the image carrier is illustrated, but the present invention is not limited to this. For example, the present invention can be applied to a configuration having a photosensitive belt.
(H03) In the above embodiment, it is desirable to provide a chamfered shape at the end of the shaft portion 1, but if the rubber tube 3 can sufficiently suppress discharge, it is also possible not to provide a chamfered shape. . Further, the chamfered shape is not limited to the arc-shaped R shape, and may be a sloped chamfered shape.

(H04) In the above-described embodiment, the number, position, and the like of each of the rolls T2b, Rt, Rf, T1y to T1k, Rw that stretch the intermediate transfer belt B can be arbitrarily changed according to the design and specifications.
(H05) In the above embodiment, the polarity of the secondary transfer voltage applied to the backup roll T2a as an example of the drive member can be changed as appropriate according to the design, specifications, and the like. For example, in the embodiment, a negatively charged toner is used and a negative secondary transfer voltage is applied to the backup roll T2a. However, a positively charged toner is used and a positive polarity is used for the backup roll T2a. It is also possible to apply a secondary transfer voltage.

(H06) In the above-described embodiment, specific numerical values and constituent materials of each member can be arbitrarily changed according to design, specifications, and the like.

1 ... the base,
3 ... surface layer,
B: Endless belt-shaped image carrier,
L ... Projection amount
S ... medium
T2a: driving member,
T2b: transfer member,
U: Image forming apparatus.

Claims (4)

An endless belt-shaped image carrier on which an image is held on the surface;
A driving member that supports the image carrier and rotates the image carrier by being driven by a drive source;
A transfer member disposed opposite to the driving member with the image carrier interposed therebetween, and transferring the image on the surface of the image carrier to a medium, covering a conductive base and the surface of the base; A surface layer having a volume resistivity higher than that of the base, and the transfer member in which the axial length of the surface layer is formed longer than the axial length of the base, and
An image forming apparatus comprising: 2. The image according to claim 1, wherein an amount by which the surface layer protrudes from an end of the base in the axial direction is set to a length of 2.75 mm or more and not more than a thickness of the surface layer. Forming equipment. The base having a chamfered end in the axial direction;
The image forming apparatus according to claim 1, further comprising: A transfer member disposed opposite to the drive member for rotating the endless belt-shaped image holding member with the image holding member interposed therebetween, and transferring the image on the surface of the image holding member to a medium;
A conductive base;
A surface layer covering the surface of the base and having a higher volume resistivity than the base, the surface layer being formed longer than the axial length of the base; and
A transfer member comprising:

Images